1. Technical Field
This invention relates to an apparatus for diminishing the amount of nitrogen oxides (NO.sub.x) in the exhaust gases of an automobile.
2. Background Art
There is known an apparatus which is designed for diminishing the amount of NO.sub.x in the exhaust gases of a diesel engine by supplying a reducing agent, such as ammonia, into the exhaust gases. For example, the Japanese Patent Application laid open under No. 83816/1989 discloses an by an NO.sub.x analyzer, and blows ammonia into the exhaust gases apparatus which detects the amount of NO.sub.x in exhaust gases in accordance with the amount of NO as detected. The use of ammonia, however, calls for a great deal of care, as it has an objectionable odor.
There is also known an apparatus which relies upon a catalytic converter incorporated in the exhaust system of an automobile for diminishing the amount of NO.sub.x in its exhaust gases. The catalytic converter relies upon hydrocarbon for its reducing action, but the exhaust gases do not contain a sufficiently large amount of hydrocarbon for the action of the catalytic converter. Therefore, the known apparatus fails to diminish the amount of NO.sub.x effectively.